The difference between substr and substring

SUBSTR and substring are both JS intercept string functions, the two uses are very similar, the following is the syntax of the two examples:

Substr method

Returns a substring of the specified length starting at the specified position.
Stringvar.substr (start [, length])

Parameters
Stringvar
Required option. The string literal or string object to extract the substring from.
Start
Required option. The starting position of the desired substring. The index of the first character in the string is 0.
Length
Options are available. The number of characters that should be included in the returned substring.

Description
If length is 0 or negative, an empty string is returned. If this argument is not specified, the substring continues to the end of the stringvar.

Sample code

function Substrdemo () {
var s, SS; Declares a variable.
var s = "The rain in Spain falls mainly in the plain.";
SS = S.substr (12, 5); Gets a substring.
return (SS); Returns "Spain".
}

Substring method

Returns a substring at the specified position in a string object.
Strvariable.substring (start, end)

"String Literal". Substring (start, end)

Parameters
Start
Indicates the starting position of the substring, starting at 0.
End
Indicates the ending position of the substring, starting at 0.

Description
The substring method returns a string containing a substring from start to last (without end).
The substring method uses the smaller values from start and end as the starting point for the substring. For example, strvar.substring (0, 3) and strvar.substring (3, 0) will return the same substring.
If start or end is NaN or negative, replace it with 0.
The length of the substring equals the absolute value of the difference between start and end. For example, the length of the substring returned in strvar.substring (0, 3) and strvar.substring (3, 0) is 3.

Sample code

function Substringdemo () {
var SS; Declares a variable.
var s = "The rain in Spain falls mainly in the plain.";
SS = S.substring (12, 17); Takes a substring.
return (SS); Returns a substring.
}

Note: When you apply substr and substring two functions to intercept a string with spaces, the length is one character length per space. For example:

var a = "I am shi huan!"; A.substring (0, 5). The value of length is 5, not 4,

But alert (a.substring (0, 5)), the value is I am, so in the alert ("I am" = = a.substring (0, 5));

The wait is false, alert ("I am" = = a.substring (0, 4)) is true.

The difference between substr and substring